1. Field of the Invention
The present invention relates to a diode and a display device including the diode.
2. Description of the Related Art
In recent years, techniques to form thin film transistors using a semiconductor thin film (with a thickness of approximately several tens to several hundreds of nanometers) which is formed over a substrate having an insulating surface have attracted attention. A thin film transistor is broadly applied to electronic devices such as an IC and an electrooptic device, and particularly, a thin film transistor as a switching element of an image display device is expected to be developed quickly.
A thin film transistor using an amorphous semiconductor film, a thin film transistor using a polycrystalline semiconductor film in which a diameter of the crystal grain is 100 nm or more, or the like is used as a switching element in an image display device. As a method of forming a polycrystalline semiconductor film, there is known a technique in which a pulsed excimer laser beam is shaped into a linear laser beam by an optical system and an amorphous silicon film is irradiated and scanned with the linear laser beam, so that the amorphous silicon film is crystallized.
Furthermore, as a switching element in an image display device, a thin film transistor using a microcrystalline semiconductor film in which a diameter of the crystal grain is about 1 nm to 100 nm is used (see Patent Document 1: Japanese Published Patent Application No. H4-242724 and Patent Document 2: Japanese Published Patent Application No. 2005-49832).